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How long will your battery last?

Tick the devices that must stay on while the power is out. We tell you what size battery you need, and which stations can do it.

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1What needs to stay on?

Tick your devices. The numbers are averages: if you know yours, change them.

2For how long?

Most official advice says to plan for 3 days.

You need a battery of
–
Per day
–
All on at once
–

How we work it out: battery Wh × 0.85 ÷ (device watts + 10 W)

These stations can do it

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    In short: a 1,000 Wh battery runs an internet router for about 43 hours, and a fridge for about 15 hours.

    How we work it out

    We take the battery size (in Wh), remove 15% for losses, and divide by what your devices use (in watts). The watts are written on each device’s label. In the calculator we put averages you can change.

    What a 1,000 Wh battery can run One device plugged in at a time
    1. LED lamp 8 W 47 h
    2. Internet router 10 W 43 h
    3. CPAP machine 12 W 39 h
    4. Fridge 45 W 15 h
    5. Laptop 60 W 12 h
    6. LED TV 80 W 9.4 h
    7. Microwave 1200 W 42 min
    8. Electric kettle 2000 W 25 min

    How we count: 1,000 Wh × 0.85 ÷ (device watts + 10 W). These are average watts. Your device may use more or less.

    How to plug in when the power is out
    Fridge Station

    YesThe device plugs into the station

    Station Wall outlet

    NeverSending the station’s power into a wall outlet or your home’s wiring

    Power would flow back into the power lines. That is dangerous for you and for the people fixing them.

    Questions

    Why multiply by 0.85?

    Some energy is lost when the battery turns into power for your outlets. So we only count 85% of the battery the brand gives. It is a careful estimate. And the station itself uses about 10 W while its outlets are on, so we add 10 W to your devices.

    Does the calculator count the power a fridge needs to start?

    Yes. A fridge needs a lot of power for a second when it starts. We only suggest stations strong enough for that.

    Can I connect the station to my home’s wiring?

    No. Plug your devices straight into the station. Sending its power into a wall outlet or your home’s wiring is dangerous for you and for the people fixing the power lines.